BareMetal is an open source 64-bit OS for x86-64 based computers. It is written in Assembly, and applications can be written in Assembly or C/C++. It's aimed at three target segments (High Performance Computing, Embedded Applications, and Education). It's also designed to be simple, and it's really small. Under 16Kb small. Version 0.4.8 was released recently, which includes updates to the C application library, updated documentation, and better support for SMP. It's good to see some innovation in the startup/hobbyist OS space. We wish them well!

The Kernel binary (which includes the kernel itself, the CLI, as well as all of the system calls) is 16KiB. In reality it is actually much smaller as the binary is padded out to 16KiB. The compiled binary without padding is 10576 bytes as of 0.4.8

- Ian Seyler @ Return Infinity

Reminds me of the days of the Atari ST (1986 and later), when the entire OS fit into 192Kbytes of ROM.

If you were to do a 64-bit BareMetal OS version of the Atari ST TOS/GEM, I wonder if you could STILL do it in that amount of space (or less)! I think it might well be VERY possible... and it would be on a 64-bit computer!

You think the Atari ST was fast for it's day? This type of system would blister the surface of the sun, it'd be so fast! :-D